1. Field of the Invention
The present invention relates to a camera module package in which via holes and bumps are flip-chip-bonded so as to correspond to each other one to one. In the camera module package, when an image sensor is bonded to the lower surface of an FPCB (flexible printed circuit board) by a flip chip, via holes passing through the FPCB are formed in positions corresponding to connection bumps provided on the upper surface of the image sensor, thereby enhancing a degree of freedom in designing an FPCB.
2. Description of the Related Art
With the recent development of mobile terminals such as portable phones and personal digital assistants (PDAs), the mobile terminals provide a phone call function and are used as multi-convergence devices. The most representative of the multi-convergence is a camera module. The resolution of the camera module changes from 300,000 pixels (VGA) to 8,000,000 pixels. Moreover, the camera module provides various additional functions, such as auto-focusing (AF) and optical zoom. Generally, camera modules are applied to various IT devices, such as camera phones, smart phones, and mobile communication terminals.
The camera modules are manufactured by using main parts of charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensors. Incident light transmitted through the lens is condensed by the image sensor and is stored as data in the memory. The stored data is displayed as an image through a display medium, such as liquid crystal display (LCD) or PC monitor.
Packaging methods of the image sensor for camera module include a chip on film (COF) method using a flip-chip bonding, a chip on board (COB) method using a wire bonding, and a chip select package (CSP). Among them, the COF packaging method and the COB packaging method are widely used.
Hereinafter, the COF packaging structure will be described briefly with reference to FIGS. 1 to 2.
FIG. 1 is an exploded perspective view of a conventional COF type camera module, and FIG. 2 is a partial sectional view of the conventional COF type camera module of FIG. 1.
Referring to FIGS. 1 and 2, the conventional camera module 1 includes an image sensor 3 for converting an image signal inputted through a lens into an electric signal, a housing 2 for supporting the image sensor 3, a lens group 4 for collecting an image signal of an object in the image sensor 3, and a barrel 5 in which the lens group 4 is stacked in multi-layers.
A flexible printed circuit board (FPCB) 6 is electrically connected to a lower portion of the housing 2. Chip components (e.g., condensers and resistors) for driving the CCD or CMOS image sensor 3 are mounted on the FPCB 6.
In the camera module 1, an anisotropic conductive film (ACF) 8 or non-conductive paste (NCP) is inserted between the FPCB 6 and the image sensor 3 in such a state that a plurality of circuit components are mounted on the FPCB 6. Then, heat and pressure are applied to electrically attach the FPCB 6 to the image sensor 3, and an IR filter 7 is attached on the FPCB.
Furthermore, in such a state that the barrel 5 and the housing 2 are provisionally screwed to each other, the assembled FPCB 6 is fixed to the bottom surface of the housing 2 by a separate adhesive.
Because the COF type camera module package does not need a space for attachment of wires, the package area and the barrel height can be reduced. Therefore, the camera module can be lightweight and slim.
In addition, because a thin film or FPCB is used, the package can be robust against external impact and can be highly reliable, and a manufacturing process of the package can be more simplified. Moreover, the COF type camera module package can attribute to high-speed processing, high density, and multiple pins, due to miniaturization and reduction in resistance.
However, as the COF type camera module package is integrated in a minimum chip size of wafer level package, a manufacturing cost increases and products may not be accurately delivered on the appointed date. Because the conventional COF package has a single-layered structure, the advantages of the miniaturization of the module package are not exhibited in the modules that use mega-pixel image sensors with various functions.
Further, when the FPCB 6 is a one-sided FPCB, a bonding surface of the FPCB 6 on which the image sensor 3 is bonded is limited to the lower surface of the FPCB 6. Therefore, the electric-connection start points of connection terminals provided in the image sensor 3 and the FPCB 6 inevitably start from the lower surface of the FPCB 6 such that a circuit-design space for the connection of the respective terminals is increased. Accordingly, the size of the FPCB 6 increases as a whole.
In order to solve the problem, a flip-chip-type module is manufactured by using a double-sided FPCB on which a plurality of via-holes are formed, as shown in FIG. 3. However, when the image sensor 3 is closely bonded to the lower surface of the double-sided FPCB 6, the plurality of via-holes are formed so as to be inevitably spaced at a distance of 150 μm from a connection bonding portion 6a such that circuit short caused by the interference between the via-holes 6b is prevented from occurring in the connection bonding portion 6a which comes in contact with a plurality of bumps 3a formed on the image sensor 3. Therefore, when a circuit using the via-holes 6b is designed, there is a spatial limitation in designing a circuit pattern.